My co-pending application, Ser. No. 973,356, filed Dec. 26, 1978, describes a lightweight, portable, military radar system especially adapted for use in jungle warfare. One of the difficulties with designing such a system is the configuration of the antenna, which must satisfy several conflicting requirements. First, because the radar cross-section of a man reaches a broad peak at about 200 MHz, the antenna must be optimized for that band. Second, because the radar system with which the antenna is to work is a Doppler system, the antenna is non-rotating; therefore, it must have as broad a beam as possible. However, notwithstanding the above, since the antenna must be portable and capable of easy erection in the field, it must not be physically large or unduly heavy.
In the aforementioned, co-pending application, which application is hereby incorporated by reference as if fully set forth herein, the antenna system employed comprises a pair of 51/2 foot log-periodic yagi antennas each having a beam-width of 12.degree.. The two yagis are angled at 45.degree. to each other to yield an effective beamwidth of 55.degree..
Unfortunately, this arrangement is unsatisfactory for actual field deployment as it is difficult to align and present a relatively large cross-section to the wind, resulting in unwanted doppler modulation in anything stronger than a light breeze.
As a solution to the above and other problems, the instant invention comprises a first, shortened, half-wave dipole and second, shortened, half-wave dipole co-axial with and contiguous to said first dipole, and first and second reflecting screens respectively positioned proximate said first and second dipoles and normal to the plane of polarization of said antenna. The invention, however, is not limited to dipole antennas; for example, horn antennas or parabolic reflector antennas may be used.
The invention and its mode of operation will be more fully understood from the following detailed description, when taken with the appended drawings, in which: